1. Field of the Invention
This invention relates to a venting cap for use in covering or masking a specific part, such as, for example, a tube or port, of a mechanical component during a high temperature processing operation such as, for example, painting, coating, plating and the like.
2. Description of Related Art
Mechanical components that are surface coated by, for example, painting or plating, often require that a specific part or feature of the component remain uncoated. Typically, a masking cap is used to cover the specific part of the mechanical component during the coating operation. Conventional masking caps, however, do not ensure that the specific part remains uncoated and free of any contaminants. These conventional masking caps are susceptible to leakage and removal under pressure.
The coating and other processing operations are often performed at high temperatures. During installation, the masking caps trap a certain amount of air when mounted on the specific part of the mechanical component. During the high temperature processing, the air that is confined within the cap expands. When this air expansion occurs, the cap can dislodge or blow off when excessive air pressure develops. The specific part is then exposed during further processing. As a result, the specific part may be subject to contamination or undesirable coating.
One solution for releasing excessive air pressure within the masking cap to prevent blow off is to add vents. These vented caps are open to the surrounding atmosphere. This arrangement, however, permits undesirable coating and other contaminants to leak onto the specific part under certain conditions. Typically, after the coating operation is completed, a negative air pressure develops within the cap and specific part during the cooling operation. This effect acts to draw contaminants including undryed coating onto the specific part.
The leaking and dislodging effects of the above-described masking caps can increase overall manufacturing costs. The specific parts that have been coated or contaminated must often be subject to additional processing to remove the coatings, etc. before use. Furthermore, the presence of this coating and contaminants may result in the complete rejection of the entire mechanical component when it is not possible or desirable to perform additional processing operations on the specific part.
Various venting cap assemblies for differing applications are known. For example, U.S. Pat. No. 2,841,166 to Auzin discloses a valve plug for an air-inflated object. The valve plug permits entry of air into the inflated object but prevents air from escaping.
U.S. Pat. No. 3,437,224 to Williams discloses a one-piece molded plastic closure provided with centering fins and stop elements that prevent the cap from completely sealing a tube opening. This arrangement allows the passage of air within the closure.
U.S. Pat. No. 3,927,798 to Loomis discloses a vented cap for a tank. The vented cap contains a spring bias baffle that permits venting in response to a sufficient build up of pressure within the tank.
U.S. Pat. No. 4,335,756 to Sharp et al. discloses a cover for enclosing an end of medical tubing. An interior of the cover includes a plurality of ribs that form a plurality of channels that permits the transmission of a sterilizing agent to enter the interior of the tubing.
U.S. Pat. No. 5,071,017 to Stuli discloses a valve closure for a hand-held dispenser. The valve closure includes a flexible diaphragm having a slit that opens upon the build up of sufficient fluid pressure within the dispenser produced by squeezing the dispenser.
U.S. Pat. No. 5,203,825 to Haynes et al. and U.S. Pat. No. 5,377,854 to Cusack disclose venting caps having one or more vent grooves therein to allow air to escape when the caps are at a first slidable position. Air is prevented from escaping when the caps are more fully inserted within the tubes.
U.S. Pat. No. 5,280,809 to Tive discloses a breather cap for protecting the ends of tubing during sterilization. The breather cap includes an inner passageway that directly connects the cap interior with the external environment.